SYMBOLCOMMON_NAMEaka. SYNONYMS
win.lurk (Back to overview)

Lurk


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References
2014-08-07SecureworksBrett Stone-Gross
@online{stonegross:20140807:malware:5bb1963, author = {Brett Stone-Gross}, title = {{Malware Analysis of the Lurk Downloader}}, date = {2014-08-07}, organization = {Secureworks}, url = {https://www.secureworks.com/research/malware-analysis-of-the-lurk-downloader}, language = {English}, urldate = {2019-12-19} } Malware Analysis of the Lurk Downloader
Lurk
Yara Rules
[TLP:WHITE] win_lurk_auto (20220516 | Detects win.lurk.)
rule win_lurk_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-05-16"
        version = "1"
        description = "Detects win.lurk."
        info = "autogenerated rule brought to you by yara-signator"
        tool = "yara-signator v0.6.0"
        signator_config = "callsandjumps;datarefs;binvalue"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.lurk"
        malpedia_rule_date = "20220513"
        malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26"
        malpedia_version = "20220516"
        malpedia_license = "CC BY-SA 4.0"
        malpedia_sharing = "TLP:WHITE"

    /* DISCLAIMER
     * The strings used in this rule have been automatically selected from the
     * disassembly of memory dumps and unpacked files, using YARA-Signator.
     * The code and documentation is published here:
     * https://github.com/fxb-cocacoding/yara-signator
     * As Malpedia is used as data source, please note that for a given
     * number of families, only single samples are documented.
     * This likely impacts the degree of generalization these rules will offer.
     * Take the described generation method also into consideration when you
     * apply the rules in your use cases and assign them confidence levels.
     */


    strings:
        $sequence_0 = { ff7508 ff15???????? 8b35???????? 50 ff7508 }
            // n = 5, score = 1100
            //   ff7508               | push                dword ptr [ebp + 8]
            //   ff15????????         |                     
            //   8b35????????         |                     
            //   50                   | push                eax
            //   ff7508               | push                dword ptr [ebp + 8]

        $sequence_1 = { 8b4508 5b 5f 5e c9 c3 55 }
            // n = 7, score = 900
            //   8b4508               | mov                 eax, dword ptr [ebp + 8]
            //   5b                   | pop                 ebx
            //   5f                   | pop                 edi
            //   5e                   | pop                 esi
            //   c9                   | leave               
            //   c3                   | ret                 
            //   55                   | push                ebp

        $sequence_2 = { 8b45fc eb3b e8???????? a1???????? }
            // n = 4, score = 800
            //   8b45fc               | mov                 eax, dword ptr [ebp - 4]
            //   eb3b                 | jmp                 0x3d
            //   e8????????           |                     
            //   a1????????           |                     

        $sequence_3 = { ff4508 8907 83c704 837d0808 72e3 }
            // n = 5, score = 800
            //   ff4508               | inc                 dword ptr [ebp + 8]
            //   8907                 | mov                 dword ptr [edi], eax
            //   83c704               | add                 edi, 4
            //   837d0808             | cmp                 dword ptr [ebp + 8], 8
            //   72e3                 | jb                  0xffffffe5

        $sequence_4 = { 6a40 8945e8 ffd7 6a50 }
            // n = 4, score = 800
            //   6a40                 | push                0x40
            //   8945e8               | mov                 dword ptr [ebp - 0x18], eax
            //   ffd7                 | call                edi
            //   6a50                 | push                0x50

        $sequence_5 = { eb09 8b45fc 83c001 8945fc 8b4dfc 3b0d???????? 0f8394000000 }
            // n = 7, score = 800
            //   eb09                 | jmp                 0xb
            //   8b45fc               | mov                 eax, dword ptr [ebp - 4]
            //   83c001               | add                 eax, 1
            //   8945fc               | mov                 dword ptr [ebp - 4], eax
            //   8b4dfc               | mov                 ecx, dword ptr [ebp - 4]
            //   3b0d????????         |                     
            //   0f8394000000         | jae                 0x9a

        $sequence_6 = { 8b45d4 40 40 8945d4 e9???????? 8b45c0 8b4dc0 }
            // n = 7, score = 800
            //   8b45d4               | mov                 eax, dword ptr [ebp - 0x2c]
            //   40                   | inc                 eax
            //   40                   | inc                 eax
            //   8945d4               | mov                 dword ptr [ebp - 0x2c], eax
            //   e9????????           |                     
            //   8b45c0               | mov                 eax, dword ptr [ebp - 0x40]
            //   8b4dc0               | mov                 ecx, dword ptr [ebp - 0x40]

        $sequence_7 = { 8b45d8 8b4dd8 03483c 894dd0 8b45d0 83c078 8945ec }
            // n = 7, score = 800
            //   8b45d8               | mov                 eax, dword ptr [ebp - 0x28]
            //   8b4dd8               | mov                 ecx, dword ptr [ebp - 0x28]
            //   03483c               | add                 ecx, dword ptr [eax + 0x3c]
            //   894dd0               | mov                 dword ptr [ebp - 0x30], ecx
            //   8b45d0               | mov                 eax, dword ptr [ebp - 0x30]
            //   83c078               | add                 eax, 0x78
            //   8945ec               | mov                 dword ptr [ebp - 0x14], eax

        $sequence_8 = { eb09 8b45ec 83c001 8945ec 8b4dd4 0fb75106 3955ec }
            // n = 7, score = 800
            //   eb09                 | jmp                 0xb
            //   8b45ec               | mov                 eax, dword ptr [ebp - 0x14]
            //   83c001               | add                 eax, 1
            //   8945ec               | mov                 dword ptr [ebp - 0x14], eax
            //   8b4dd4               | mov                 ecx, dword ptr [ebp - 0x2c]
            //   0fb75106             | movzx               edx, word ptr [ecx + 6]
            //   3955ec               | cmp                 dword ptr [ebp - 0x14], edx

        $sequence_9 = { 55 8bec 83ec0c 53 56 8b7508 0fb606 }
            // n = 7, score = 800
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   83ec0c               | sub                 esp, 0xc
            //   53                   | push                ebx
            //   56                   | push                esi
            //   8b7508               | mov                 esi, dword ptr [ebp + 8]
            //   0fb606               | movzx               eax, byte ptr [esi]

        $sequence_10 = { ff37 e8???????? 83c418 85c0 ff37 6a00 7519 }
            // n = 7, score = 800
            //   ff37                 | push                dword ptr [edi]
            //   e8????????           |                     
            //   83c418               | add                 esp, 0x18
            //   85c0                 | test                eax, eax
            //   ff37                 | push                dword ptr [edi]
            //   6a00                 | push                0
            //   7519                 | jne                 0x1b

        $sequence_11 = { 8b7e04 ff7508 037e08 ff15???????? }
            // n = 4, score = 800
            //   8b7e04               | mov                 edi, dword ptr [esi + 4]
            //   ff7508               | push                dword ptr [ebp + 8]
            //   037e08               | add                 edi, dword ptr [esi + 8]
            //   ff15????????         |                     

        $sequence_12 = { 6a1a 5f f7ff a1???????? 57 80c261 }
            // n = 6, score = 800
            //   6a1a                 | push                0x1a
            //   5f                   | pop                 edi
            //   f7ff                 | idiv                edi
            //   a1????????           |                     
            //   57                   | push                edi
            //   80c261               | add                 dl, 0x61

        $sequence_13 = { 68???????? 8d85ecfeffff 50 ff15???????? 8d85ecfeffff 50 68???????? }
            // n = 7, score = 800
            //   68????????           |                     
            //   8d85ecfeffff         | lea                 eax, [ebp - 0x114]
            //   50                   | push                eax
            //   ff15????????         |                     
            //   8d85ecfeffff         | lea                 eax, [ebp - 0x114]
            //   50                   | push                eax
            //   68????????           |                     

        $sequence_14 = { 7519 6a01 8d460b 50 e8???????? 59 }
            // n = 6, score = 800
            //   7519                 | jne                 0x1b
            //   6a01                 | push                1
            //   8d460b               | lea                 eax, [esi + 0xb]
            //   50                   | push                eax
            //   e8????????           |                     
            //   59                   | pop                 ecx

        $sequence_15 = { 8b7df8 81e7ffff0000 56 ff15???????? }
            // n = 4, score = 800
            //   8b7df8               | mov                 edi, dword ptr [ebp - 8]
            //   81e7ffff0000         | and                 edi, 0xffff
            //   56                   | push                esi
            //   ff15????????         |                     

    condition:
        7 of them and filesize < 5316608
}
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